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Low-level aerobatics
If you may permit a question from someone at the back of the aircraft (but I have handled a Chipmunk and a Cessna in the past) - am I right in thinking that low-level (under one hundred feet) aerobatics are the domain of professional display pilots, and / or the insane?
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Yup (to both). There are loads of dead people who have proved their excellence at low level aerobatics. As for the lowest level, it all depends on who you are, what you are doing and where you are doing it. The basic law is the 500' rule (from person's, vehicles, vessels and structures) and also no aerobatics over congested areas. GASIL suggests that aerobatics should be completed no lower than 3,000' AGL. Also, one shouldn't recklessly endanger and aircraft or those on the ground. To legally perform low level displays, you need a Display Authorisation and these are issued after a test of competence by a CAA examiner.
PM |
Just for reference, the lowest limit for competition aerobatics, depending on the competence level of the pilot, is between 700 and 1500 feet. Drop below that and your penalized. Drop significantly (>100') below that and you're disqualified.
For training we try to use a lower limit of 3500 feet, airspace and weather permitting. Mainly for safety, obviously, but also to limit noise on the ground. Display Aerobatics requires a DA, as mentioned, which needs to be renewed regularly - I think every year before the display season starts. And even those with DAs will very carefully plan their sequences so that that lower limit is only reached in a safe, controllable manner. Brian Lecomber has a column in Flyer Magazine and regularly writes about this sort of stuff. |
Thanks to both for swift responses. So a reference to a "barrel roll" performed "at 50ft" is at best a typo for "500ft", but probably pure bovine effluent?
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Display Authorisations for aerobatics will generally have at least two separate height minima, one for figures deemed to be aerobatic, and a lower one for a fly-by. The set of aerobatic figures which can be performed under a specific DA conform roughly to the different levels of competition aerobatics.
There are very few people around with a zero-base-height Unlimited aerobatic DA. The barrel-roll has probably killed more display pilots than all other aerobatic figures put together - I'd take your reference to "50ft" with a large dose of salt. |
Or unless you happen to be Alex Henshaw in a spitfire!
Although I think he may have qualified as both professional and display pilot while working at Castle Bromwich, flight testing spitfires. SD |
Or unless you happen to be Alex Henshaw in a spitfire! What you will often see is an aerobatic figure done at quite a high altitude but the exit dive is allowed to run out quite low for effect. e.g a loop where the normal pull out would be done at 500 ft but the pilot lets it descend much lower during the last 1/8th. This 'fools' most of the audience but gives a big safety margin for the pilot. I suspect this might be why you see "barrel rolls at 50 ft" in articles. ZA |
ZA,
Quite right - I was really referring to the OP question, not specifically to the barrel roll. I guess I was just too lazy to quote the appropriate piece! Here's his own description of a typical display sequence of about 6-7 minutes: These demonstrations varied over the years according to the audience and the conditions. Like providing a good seat at the cinema, the first thing to do if possible was to fly with the sun on the backs of the audience, so that they were not blinded all the time, and at a distance which did not make them strain their necks. Always, if I could, I operated up and down wind: if the wind was strong and one upward-rolled across it, the manoeuvre could look untidy, and sometimes would put one in the incorrect position for the next manoeuvre. As a rule the drill was to take off and not climb, but pause with the wheels coming up and the machine just clear of the ground, and at 150-160 IAS pull up slowly but firmly into a half loop, finishing with a half roll at the top. I never really liked this as one cough from the engine and I should have been in real trouble: at the roll stage I was in any case holding the machine by maximum engine power well below the normal stall and the slightest coarse handling on the controls would cause the machine to flick out. I would continue this in maybe another couple of half loops and rolls until I was over 4000 ft and then, placing myself in the correct position over the aerodrome, half roll again and go into an absolutely vertical dive with full engine and maximum revs to pull out a few feet from the ground and go into a vertical roll to the left, a vertical roll to the right and a half roll to the left with a half loop, and then pull out to repeat the manoeuvre in the opposite direction. Pulling out in another half loop in the other direction, the throttle would be snapped back and plummeting down vertically one could get in two complete aileron turns to pull out again and open the throttle to do the same thing in the other direction. Having now used up most of my height and speed, I would pull up vertically to about 1000 ft and in a tight half loop at the right moment flick the machine into a full flick roll. This I always felt was a tricky one. It took a lot of judgement to do it accurately, because very often the manoeuvre was so sudden and vicious that on checking the machine it would sometimes be slightly out of line and I knew it could look untidy. I could usually get one-and-a-half to two full flicks of a roll on the horizontal but for the sake of control and tidiness I usually settled for one, which I knew I could judge to a nicety. In practice I could get in about the same with the vertical flick rolls, but with these I found it almost impossible for me to judge when to check and come out clean. I have never seen anyone flick-roll a Spitfire and I must say that I always found it a little frightening to abuse a machine and have it flash out of your control, if only for a few seconds, like a young spirited blood-horse. On the pull-out from the flick roll sometimes I would open the engine flat out in another vertical climb and, at approximately 1200 ft, push the nose over forward then, with the engine closed, complete the half of an outside loop, usually in those days called a `bunt'. I never really liked this manoeuvre either: it was easy but required heavy pressure forward on the control column and you could not afford to misjudge at 1200 ft: with the nose going over down towards the ground the speed built up at such an alarming rate that it left no room to change your mind until it was too late. At the bottom of the inverted dive I would usually 'round off' to a few feet above the ground and then, with as much pressure as I dared use on the control column - I say 'dared' because I found it more disconcerting and frightening to 'black-out' from excessive negative `G' than I did from high loads in the positive position - I would push the machine into an almost vertical climb and, as it lost momentum from the negative 'G' position, pull the control gently over to form a half-loop, hoping as I did so that the engine would burst into life as I opened the throttle. This it usually did with a spectacular sheet of flame pluming from the exhaust stubs caused by unused fuel which had accumulated during the inverted manoeuvres. With the engine now on full power I would do a series of very low rolls left and right in front of the audience at below hangar height, finishing in the inverted position from which I would 'raise' the undercarriage, pull into a tight, fast engine-off turn and lower the flaps, as I touched down for the landing. |
Two-mistakes high
I once had a very experienced pilot tell me that when doing aerobatics, one should always be "two-mistakes" high, especially if trying something new. That was high enough to screw up a maneuver (mistake no. 1) and screw up the recovery attempt (mistake no. 2), and still have altitude left to sort it out. :)
By and large, history would suggest a floor of 3,000 ft AGL is about two-mistakes high! |
Didn't someone in a Yak attempt a low level barrel roll at Bournemouth several years ago as their final manoeuvre in a joy ride flight (literally).....
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Saab, having read "Sigh for a Merlin" - I wish someone had filmed one of Alex Henshaw's low-level Spitfire displays - an outside loop from 1200 ft?!
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Two mistake rule is correct.
The worst position to be in is upside down and nose low at low level, as in doing a barrel roll from low level. It's easy to get in this position if you don't pitch up enough at the start of a barrel roll. I have a sketch in my aerobatics manual of what it looks like..and it's most likely the last thing you will ever see. That's why the victory roll and "garbage roll" (on takeoff barrel roll) were prohibited to military airmen in and after WWII. |
one should always be "two-mistakes" high |
Well, I know a nice Extra guy, who's got a personal min altitude of 50 feet. He used to be an RAF pilot long ago.
My training started at 2800, and now I am working my way down in 100 feet steps. I think you should know your weaker points and keep from showing those at low altitude. Plus there are some manoeuvres that are notorious killers at low altitudes. |
As for 100 feet and below, it sounds a bit unnecessary apart from low passes, which are not aerobatics. As for safety, if I know that since I can remember myself I've never lost any altitude in e.g rolls (and in the worst cases I gained altitude instead of losing) then I probably wouldn't be too nervous about doing the same stuff at 100 feet.
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I always enjoyed watching Brian Lecomber's displays, because they didn't scare me!!. I have seen too many people [11] die at Airshows.
I spoke to him sheltering under a rainsoaked wing once, and asked him why, despite the low levels he attained, I was not apprehensive. He winked and said that the answer was always in the pull-out. If you watch some of these idiots [his words] they are still pulling hard at 100 feet or less. He said he is never pulling hard at low level, and ALWAYS had the option of pulling harder, therefore he could get his manouevers to appear more spectacular than they were, but still with the safety margin. Drank half a bottle of his scotch at his house once. Still recall the hang-over! If any of you get to OShkosh and watch the aerobatics there, you one must wonder how any of them survive for more than a couple of years at it. [Some don't of course.] |
Interesting thread. Note that the rules vary from place to place. I happen to have an aerobatic endorsement from my country of license origin; that gives me a legal 'deck' of 3000agl; any lower requires additional waivers/authorities.
However, in the UK there is no aeros endorsement - as I understand it, there is no special requirement for aeros, other than the requirement for not over a built up area. The usual 'land clear', and 500ft rule apply. Sidenote here, the 500ft rule does *not* say 500ft above, it says 500ft clear - by my understanding, technically that *could* be 500ft laterally, and 1ft off the ground - if you're very sure nobody is within 500ft, you're technically OK. I consider that more a curio though - 500ft is plenty low enough, in fact, as far as I'm concerned, the 3000 deck is just fine.. I don't have the first idea how the DA requirements are worked, nor do I especially care. Aeros for me (the pilot) is just as interesting at height, and a sight less likely to become terminal; I have spun (a glider) from well below 500ft as a checkout exercise - it's a very very different experience I can assure anyone. To the OP's question, Yes, and YES - in this case the rules and regs are a bit of a side-matter. |
Sidenote here, the 500ft rule does *not* say 500ft above, it says 500ft clear - by my understanding, technically that *could* be 500ft laterally, and 1ft off the ground - if you're very sure nobody is within 500ft, you're technically OK. Skimming over the wavetops, that means you've got to be sure no divers underwater, less than 500 ft deep, or no structures less than 500 ft deep. Over land, no tunnels etc. Legally, if you were to find a structure with a 1000ft gap in it, you could even fly through this gap if you wanted to. Maybe that's the reason that they created a no-fly zone around the Millau bridge - otherwise you could legally fly below it. Millau Viaduct - Wikipedia, the free encyclopedia |
Low level aeros are very specialised and for display purposes are covered by the DA system with all sorts of controls. (Good old EASA have rejected the UK DA system as it was invented here and saves lives:ugh:) The actual techniques are modified to increase safety margins because low level you don't have many options. The comment above about completing the maneover then adjusting the exit for effect (with light pull) is an example.
Barrell Rolls have a bad history and are not flown in the classical way to make them safer without spoiling the look too much. Brian used to do a Roll On Take On at 30 feet (didn't like it so much in the Extra as he could see where he was going :) ). He managed to display for 25 years professionally so it can be done with the right focus. DA pilots must have practiced their display 3 times before every display (and sign to say so) but have mentally rehersed many times more. Not something to be entertained without a lot of training, supervision and compliance with the associated rules. |
If any of you get to Oshkosh and watch the aerobatics there, you one must wonder how any of them survive for more than a couple of years at it Lecomber was always a joy to watch, wish he was still campaigning on the circuit. By the way, it's not just the ground that can snag you - I can think of at least three people who have hit a tree after pulling out... |
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